In general, a magnetic disk drive, such as a hard disk drive (HDD), comprises a magnetic disk, spindle motor for rotating the magnetic disk, magnetic head for reading data from and writing data to the magnetic disk, carriage supporting the magnetic head, voice coil motor for driving the carriage, board unit, etc. These elements are accommodated in a substantially sealed housing. A drive section, comprising the spindle motor, carriage, voice coil motor, etc., and the board unit are mounted on the bottom wall of the housing.
In the magnetic disk drive, the rotation speed of the magnetic disk must be increased to achieve high-speed data processing. If the magnetic disk rotates at high speed, however, airflow is produced in the direction of rotation of the magnetic disk, and a phenomenon called disk flutter occurs such that the magnetic disk is caused to vibrate by turbulence of the airflow. Further, airflow disturbance acts on the carriage that supports the magnetic head, thereby displacing the carriage. In this case, the positioning accuracy of the magnetic head relative to the magnetic disk is reduced, so that the recording density cannot be improved. In order to suppress the occurrence of air turbulence due to high-speed rotation of the magnetic disk, a magnetic disk drive has been proposed in which a spoiler for use as a baffle plate is disposed between magnetic disks.
In Enterprise and Nearline HDDs used for server application, moreover, a strongly-magnetized magnetic circuit is used for the voice coil motor to facilitate high-speed seek of the carriage. In a typical conventional structure, outward leakage of magnetic flux from this magnetic circuit is prevented by a return yoke configuration formed by bending a top or bottom yoke of the voice coil motor.
In the case where the return yoke is used to prevent leakage of magnetic flux toward the magnetic disk, the return yoke must be located near the magnetic disk. If the spoiler is also assumed to be used in this case, consideration must be given to interference between the return yoke and spoiler during assembly and installation. If the conventional configuration is expected to allow the use of the spoiler while preventing leakage of magnetic flux, the installation of the spoiler is very difficult, and the shapes of the spoiler and yoke and methods for securing them are restricted in design.